Hey buddy!
I just bought a new Si, looks quite like that but 5 door!
Theres loadsa things you can do, depends what you're wanting really!
Atm i'm thinking of de-globing, lowering, window tints, alloys and front splitter.
I'd highly suggest signing up for a full membership though if you wanna start modding. Theres loadsa advice in the "How To" section, and some pretty good discounts etc. I've learnt pretty much everything I know about modding since I joined up, so its pretty worthwhile.
Welcome to the crew.
B